We recieve error messages when uploading media in the K2 plugin for Joomla.

Error:
PHP Warning: preg_match(): Compilation failed: invalid range in character class at offset 7 in /public/sites/www.jcctuinenparkmachines.nl/administrator/components/com_k2/lib/class.upload.php on line 2910
/public/sites/www.jcctuinenparkmachines.nl/administrator/components/com_k2/lib/class.upload.php on line 2950
/public/sites/www.jcctuinenparkmachines.nl/administrator/components/com_k2/lib/class.upload.php on line 2977
/public/sites/www.jcctuinenparkmachines.nl/administrator/components/com_k2/lib/class.upload.php on line 3004
/public/sites/www.jcctuinenparkmachines.nl/administrator/components/com_k2/lib/class.upload.php on line 3022

What to do to solve this?
Thanks for your answer.

Hello,
Which version of K2 and Joomla! are you using?

Using Joomla 3.4.8 and K2 2.6.9

We updated both but then the site went ballistic because of the custom made plugins.

This error only shows up at two items:
www.jcctuinenparkmachines.nl/gazonmaaiers/stiga/batterij/item/500-combi-50-s-ae
www.jcctuinenparkmachines.nl/gazonmaaiers/stiga/electrisch/item/503-combi-48-es

So we loaded the picture direct in the text window, but that is not the way it should be.
Do you know any solution?

It's about the first line in this code:
if (preg_match("/^([\.-\w]+)\/([\.-\w]+)(.*)$/i", $this->file_src_mime)) {
$this->file_src_mime = preg_replace("/^([\.-\w]+)\/([\.-\w]+)(.*)$/i", '$1/$2', $this->file_src_mime);
$this->log .= '-&nbsp;MIME validated as ' . $this->file_src_mime . '<br />';
} else {
$this->file_src_mime = null;

What to do?

Can you try updating to 2.7.0 or 2.7.1 (DEV version)?
Please backup before updating.

As I told earlier we updated to 2.7.0, but still it didn't work.
What to do?

Maybe something to change in the code?
Other items do upload fine for the pictures.

Hi,
What is your PHP version ?

PHP version 5.6.17-1

What to do now?

If I understood correctly you mentioned that this error occured with 2 specific K2 items. Can you share the file(s) that you tried to upload in order for me to make some tests and try to reproduce the issue ?